Protection device of electric power steering system and electric power steering system including the same

Abstract

A protection device for an electric power steering (EPS) system may include a first comparator for comparing a high voltage potential of a power supply of an electric power steering system with a threshold high voltage, a second comparator for comparing the high voltage potential of the power supply with a threshold low voltage, an exclusive switching unit for outputting an enable signal or a disable signal according to whether a first comparison output signal of the first comparator and a second comparison output signal of the second comparator are the same, and a battery cutoff device for switching a voltage supply of the power supply to an electronic control unit of the electric power steering system according to the enable signal or the disable signal.

What is claimed is: 
     
       1. An electric power steering system comprising:
 a power supply; 
 an electronic control unit configured to control driving of a steering motor based on a supply voltage applied from the power supply; 
 a steering motor which is driven by the electronic control unit to electrically assist or operate a steering of a vehicle; and 
 a protection device including a protection circuit configured to prevent an abnormal voltage from being applied to the electronic control unit, 
 wherein the protection circuit comprises, 
 a first comparator for comparing a high voltage potential of the power supply with a threshold high voltage; 
 a second comparator for comparing the high voltage potential of the power supply with a threshold low voltage; 
 an exclusive switching unit configured to output an enable signal or a disable signal according to whether a first comparison output signal of the first comparator and a second comparison output signal of the second comparator are the same; and 
 a battery cutoff device configured to switch a voltage supply of the power supply to the electronic control unit according to the enable signal or the disable signal. 
 
     
     
       2. The electric power steering system of  claim 1 , wherein the exclusive switching unit is an XOR gate element. 
     
     
       3. The electric power steering system of  claim 2 , wherein the XOR gate element outputs the disable signal in response to determining that the first comparison output signal and the second comparison output signal are the same, and outputs the enable signal in response to determining that the first comparison output signal and the second comparison output signal are different. 
     
     
       4. The electric power steering system of  claim 1 , wherein the battery cutoff device includes a gate receiving the enable signal, a source receiving a voltage of the power supply, and a field effect transistor (FET) including a drain that outputs an output voltage supplied to the electronic control unit. 
     
     
       5. The electric power steering system of  claim 1 , wherein the protection circuit further comprises a first resistance element disposed between a first-1 input terminal of the first comparator for inputting the high voltage potential and a first-2 input terminal to which the threshold high voltage is input, and a first diode element disposed between the first-2 input terminal and a ground. 
     
     
       6. The electric power steering system of  claim 5 , wherein the protection circuit further comprises a second resistance element disposed between a second-1 input terminal of the second comparator for inputting the high voltage potential and a second-2 input terminal to which the threshold low voltage is input, and a second diode element disposed between the second-2 input terminal and the ground. 
     
     
       7. The electric power steering system of  claim 6 , wherein a value of the threshold high voltage is determined by the first resistance element, and a value of the threshold low voltage is determined by the second resistance element. 
     
     
       8. The electric power steering system of  claim 1 , wherein, in response to determining that the supply voltage of the power supply is equal to or higher than the threshold high voltage, the battery cutoff device is turned off and power supply to the electronic control unit is cut off. 
     
     
       9. The electric power steering system of  claim 1 , wherein, in response to determining that the supply voltage of the power supply is less than or equal to the threshold low voltage, the battery cutoff device is turned off and power supply to the electronic control unit is cut off. 
     
     
       10. The electric power steering system of  claim 7 , wherein a resistance value of the first resistance element is smaller than a resistance value of the second resistance element. 
     
     
       11. A protection device for an electric power steering system comprising:
 a first comparator configured to compare a high voltage potential of a power supply of an electric power steering system with a threshold high voltage; 
 a second comparator configured to compare the high voltage potential of the power supply with a threshold low voltage; 
 an exclusive switching unit configured to output an enable signal or a disable signal according to whether a first comparison output signal of the first comparator and a second comparison output signal of the second comparator are the same; and 
 a battery cutoff device configured to switch a voltage supply of the power supply to an electronic control unit of the electric power steering system according to the enable signal or the disable signal. 
 
     
     
       12. The protection device of  claim 11 , wherein the exclusive switching unit is an XOR gate element. 
     
     
       13. The protection device of  claim 12 , wherein the XOR gate element outputs the disable signal in response to determining that the first comparison output signal and the second comparison output signal are the same, and outputs the enable signal in response to determining that the first comparison output signal and the second comparison output signal are different. 
     
     
       14. The protection device of  claim 11 , wherein the battery cutoff device includes a gate receiving the enable signal, a source receiving a voltage of the power supply, and a field effect transistor (FET) including a drain that outputs an output voltage supplied to the electronic control unit. 
     
     
       15. The protection device of  claim 11 , further comprising:
 a first resistance element disposed between a first-1 input terminal of the first comparator for inputting the high voltage potential and a first-2 input terminal to which the threshold high voltage is input; and 
 a first diode element disposed between the first-2 input terminal and a ground. 
 
     
     
       16. The protection device of  claim 15 , further comprising:
 a second resistance element disposed between a second-1 input terminal of the second comparator for inputting the high voltage potential and a second-2 input terminal to which the threshold low voltage is input; and 
 a second diode element disposed between the second-2 input terminal and the ground. 
 
     
     
       17. The protection device of  claim 16 , wherein a value of the threshold high voltage is determined by the first resistance element, and a value of the threshold low voltage is determined by the second resistance element. 
     
     
       18. The protection device of  claim 11 , wherein, in response to determining that the supply voltage of the power supply is equal to or higher than the threshold high voltage, the battery cutoff device is turned off and power supply to the electronic control unit is cut off. 
     
     
       19. The protection device of  claim 11 , wherein, in response to determining that the supply voltage of the power supply is less than or equal to the threshold low voltage, the battery cutoff device is turned off and power supply to the electronic control unit is cut off. 
     
     
       20. The protection device of  claim 17 , wherein a resistance value of the first resistance element is smaller than a resistance value of the second resistance element.